Polycarbonate resins have been widely used as an engineering plastic material due to their high impact resistance, self-extinguishing properties, dimensional stability and high thermo-resistance, as compared to conventional polymers. Polycarbonate resins require flame retardancy and a good appearance when used in housings of electronic devices and office automation devices. However, polycarbonate resins do not have good external scratch resistance since they have a low pencil hardness of 2B or so. In order to improve the scratch resistance of polycarbonate resins, acrylic resins which have good scratch resistance can be mixed with a polycarbonate resin or coated on the surface of a polycarbonate article.
U.S. Pat. No. 4,319,003 and EP 297285 disclose an opaque blend of a mixture of polycarbonate and polymethylmethacrylate (PMMA). However, the composition reduces transparency and experiences a significant drop in heat-resistance.
U.S. Pat. Nos. 4,027,073 and 4,455,205 disclose a method of coating a silicone based resin and acrylic based resin having good scratch resistance on the surface of a polycarbonate article. However, the method requires an extra coating step and equipment, which raises the cost.
In addition, U.S. Published Application Nos. 2008/0015292 and 2008/0015291 disclose a composition comprising polycarbonate copolymer and bisphenol A polycarbonate derived from dimethyl bisphenol cyclohexane, which can have good scratch resistance. However, the product cost can be high and the impact strength can be significantly reduced.